1. Field of the Invention
The present invention relates to a motor driving control device, and more particularly, to a motor driving control device which can be suitably used in an input apparatus with an operation feeling imparting function of imparting an operation feeling to a manual operating member connected to a rotational shaft of a motor.
2. Description of the Related Art
In the related art, in a motor driving control device, which selectively rotates a direct-current motor in one direction or in a reverse direction, a bridge driving circuit, in which four switching elements are brought into H-type bridge connection, together with the direct-current motor, is used. In this case, the H-type bridge driving circuit is configured such that first and second switching elements are connected between a power supply and a reference potential point in series, third and fourth switching elements are connected between the power supply and the reference potential point in series and in parallel with the first and second switching elements, and the direct-current motor is connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements. And then, in case of rotating the direct-current motor in one direction, the first and fourth switching elements may be turned on, and the second and third switching elements may be turned off. In contrast, in case of rotating the motor in the reverse direction, the first and fourth switching elements may be turned off, and the second and third switching elements may be turned on.
Various H-type bridge driving circuits for driving the direct-current motor are known till now. As the representative one, a motor driving circuit disclosed in JP-A-05-236797 or JP-A-10-080194 can be exemplified.
FIGS. 10A and 10B are circuit diagrams showing the configuration of the motor driving circuit disclosed in JP-A-05-236797. FIG. 10A shows a first configuration example and FIG. 10B shows a second configuration example.
As shown in FIG. 10A, in the first configuration example of the motor driving circuit, a pair of FETs 41 and 42 and a backflow preventing diodes 43, which are connected in series between points A and B, a pair of FETs 44 and 45 and a backflow preventing diode 46, which are connected in series between the points A and B, a direct-current motor 47 connected between a connection point of the FETs 41 and 42 and a connection point of the FETs 44 and 45, and a current detection resistor 48 connected between the point B and a ground point constitute an H-type bridge driving circuit. Further, in the H-type bridge driving circuit, a power supply 49 is connected between the point A and the ground point, and reflux diodes 50 and 51 are correspondingly connected between both ends of the direct-current motor 47 and the ground point. In addition, a constant current control circuit 52 that controls and drives the pair of FETS 41 and 42 are provided. In this case, from the nature of the element, the FETs 41 and 42 have parasitic diodes 41(1) and 42(1) therein, respectively. Similarly, the FETs 44 and 45 have parasitic diodes 44(1) and 45(1), respectively.
The motor driving circuit according to the first configuration example operates as follows.
At the time of forward rotation of the direct-current motor 47, a high-level driving signal is supplied to the FET 41 and the FET 45, and a low-level driving signal is supplied to the FET 44 and the FET 42, such that the FETS 41 and 45 are turned on and the FETs 44 and 42 are turned off. And then, a current flows from the FET 41 to the FET 45 through the direct-current motor 47, and this current serves as a forward rotation current of the direct-current motor 47. On the other hand, at the time of reverse rotation of the direct-current motor 47, the high-level driving signal is supplied to the FET 44 and the FET 42, and the low-level driving signal is supplied to the FET 41 and the FET 45, such that the FETs 44 and 42 are turned on and the FETs 41 and 45 are turned off. And then, a current flows from the FET 44 to the FET 42 through the direct-current motor 47, and this current serves as a reverse rotation current of the direct-current motor 47.
At the time of forward rotation or reverse rotation of the direct-current motor 47, if a PWM signal is supplied from the constant current control circuit 52 as a driving signal, an average current value of the forward rotation current of the direct-current motor 47 flowing in the FET 41 or an average current value of the reverse rotation current of the direct-current motor 47 flowing in the FET 44 is changed corresponding to a pulse duty indicating an on-to-off ratio of the PWM signal. These average current values are detected by the current detection resistor 48, and the detection result is supplied to the constant current control circuit 52. At this time, the constant current control circuit 52 controls and adjusts the pulse duty of the PWM signal such that the detected average current value becomes a target current value.
The motor driving circuit according to the first configuration example uses the FETS 41, 42, 44, and 45 with the parasitic diodes formed therein as the switching elements. Accordingly, when the FETS 42 and 45 disposed close to the ground point are turned off, in order to prevent a flux current from flowing through the parasitic diodes 42(1) and 45(1), the backflow preventing diodes 43 and 46 are additionally connected in series to the FETs 42 and 45, respectively.
In contrast, as shown in FIG. 10B, in the second configuration example of the motor driving circuit, instead of the FETs 42 and 45 disposed close to the ground point from the FETs 41, 42, 44, and 45 in the first configuration example, Darlington bipolar transistors 42′ and 45′, in which parasitic diodes are not formed, are used. That is, the backflow preventing diodes 43 and 46, which were used in the first configuration example, are eliminated. Moreover, in FIG. 10B, the same parts as those shown in FIG. 10A are represented by the same reference numerals.
The operation of the second configuration example of the motor driving circuit is primarily the almost same as the operation of the above-described first configuration example, and the description thereof will be omitted. In this case, the motor driving circuit according to the second configuration example does not use the backflow preventing diodes 43 and 46, thereby reducing the number of circuit components to be used by that amount.
Further, FIG. 11 is a circuit diagram showing the configuration of the motor driving circuit disclosed in JP-A-10-080194 (corresponding U.S. Pat. No. 6,066,930).
As shown in FIG. 11, in the motor driving circuit, a pair of complementary transistors 61 and 63 connected between points A and B in series, a pair of complementary transistors 62 and 64 connected between the points A and B in series, a motor 65 connected between a connection point of the transistors 61 and 63 and a connection point of the transistors 62 and 64, and a current detection resistor 66 connected between the point B and a ground point constitute an H-type bridge driving circuit. Further, in the H-type bridge driving circuit, a power supply 67 is connected to the point A and the ground point, reflux diodes 68 and 69 are connected in parallel with the transistors 61 and 62, respectively, and reflux diodes 70 and 71 are correspondingly connected between both ends of the motor 65 and the ground point. In addition, a control circuit 72 that controls and drives the four transistors 61 to 64 is provided, and a comparator 74 that compares the detection voltage of the current detection resistor 66 with a reference voltage of a direct-current power supply 73 and supplies the comparison output to the control circuit 72.
The motor driving circuit having the above-described configuration operates as follows.
At the time of forward rotation of the motor 65, a driving signal having a polarity for turning on the transistor 61 and a signal having a polarity for turning on the transistor 64, and a driving signal having a polarity for turning off the transistor 62 and a signal having a polarity for turning off the transistor 63 are supplied from the control circuit 72, such that the transistors 61 and 64 are turned on and the transistors 62 and 63 are turned off. And then, a current flows from the transistor 61 to the transistor 64 through the motor 65, and this current serves as a forward rotation current. On the other hand, at the time of reverse rotation of the motor 65, a driving signal having a polarity for turning on the transistor 62 and a signal having a polarity for turning on the transistor 63, and a driving signal having a polarity for turning off the transistor 61 and a signal having a polarity for turning off the transistor 64 are supplied from the control circuit 72, such that the transistors 61 and 64 are turned on and the transistors 62 and 63 are turned off. And then, a current flows from the transistor 62 to the transistor 63 through the motor 65, and this current serves as a reverse rotation current.
At the time of forward rotation or reverse rotation of the motor 65, the current of the motor 65 is detected by the current detection resistor 66, and a detection voltage obtained from the current detection resistor 66 is supplied to the comparator 74, and the comparator 74 compares the detection voltage with a reference voltage to be output from the power supply 73. And then, when the detection voltage is larger than the reference voltage, the comparator 74 inverts a polarity of its output voltage, and the output voltage having an inverted polarity is supplied to the control circuit 72, such that forward rotation or reverse rotation driving of the motor 65 stops. As regards the stop of driving of the motor 65 at this time, two transistors, which were just immediately turned on, may be simultaneously turned off, or one of the two transistors may be turned off. Next, when predetermined time lapses, the control circuit 72 restarts forward rotation or reverse rotation of the motor 65, and then the current of the motor 65 is sequentially increased. At this time, the increased current of the motor 65 is detected by the current detection resistor 66. Subsequently, the above-described operation is repeatedly executed. Accordingly, the average current value of the current flowing in the motor 65 is made almost constant.
In addition, as an operation input apparatus in which such a motor driving circuit is used thereby to form an input apparatus with an operation feeling imparting function, for example, an operation input apparatus disclosed in JP-A-2003-22159 (corresponding U.S. Pat. No. 6,854,352) is exemplified. The operation input apparatus disclosed in JP-A-2003-22159 uses two motor driving circuits for one tiltable operating member, and thus, when the tiltable operating member operates, an operation feeling is imparted to the operating member through the motors of the two motor driving circuits. Therefore, the operation input apparatus has two driving bodies that are disposed to cross to the tiltable operating member at right angles, and two driving levers that are connected to the two driving bodies, respectively, and perform a seesaw operation in response to a tilt operation of the tiltable operating member. In this case, the shafts of the motors are combined with the two driving levers, respectively, such that the motors individually operate corresponding to the tilt operation of the tiltable operating member.
In the first configuration example, the motor driving circuit disclosed in JP-A-05-236797 uses the four FETs as the switching elements that control driving and stop of the motor, and the two backflow preventing diodes for preventing the reflux current are connected in series to the two FETs connected to the ground, respectively. Accordingly, the number of circuit components to be used is increased by that amount, and manufacturing costs tend to be increased. Further, in the second configuration example, instead of the two FETs connected to the ground, the two Darlington bipolar transistors are used, thereby avoiding the connection of the two backflow preventing diodes. However, a loss when the Darlington bipolar transistor is turned on is larger than a loss when the FET is turned on, and thus switching operation efficiency is slightly decreased.
Further, in the motor driving circuit disclosed in JP-A-10-080194, the four bipolar transistors are used as the switching elements that control driving and stop of the motor. In this case, if the value of the current flowing in the motor exceeds a predetermined value, after predetermined time lapses from that time, the two bipolar transistors are turned on. Accordingly, the time, at which the two bipolar transistors are turned on, depends on an increase rate of the value of the current flowing in the motor, and the timing at which the transistor is turned on is not made by a constant interval. Therefore, when the two bipolar transistors are turned on or off, a jarring noise may occur.
In addition, in the input apparatus with an operation feeling imparting function disclosed in JP-A-2003-22159, the driving timings of the two motors are not considered. Accordingly, when driving time of the two motors overlap, a large current temporarily flows in the two motors from the power supply, and thus ripple components of the power supply current may be increased. Further, the capacity of the power supply needs to be increased.